This invention relates to agricultural irrigation sprinklers and more specifically to large volume sprinkler heads of the rotary step-by-step type that are capable of being operated in a reversing part circle mode. Sprinkler heads of this type are disclosed in U.S. Pat. Nos. 3,559,887; 3,744,720; 4,153,202; 4,193,548; 4,342,424; and 4,720,045. The invention described herein is applicable to sprinkler heads where the part circle mode of operation includes a cycle having an operative or forward step-by-step rotary movement through a part circle arc of travel and a similar speed step-by-step reverse movement through the same arc of travel.
Large volume, part circle sprinklers are often used on traveling irrigation systems (travelers), or as the last (i.e., radially outermost) sprinkler (also known as an end gun) on pivot irrigation systems. In either case, there is a need to change the arc of travel at various points during a typical operation. For example, when a large volume sprinkler is used on a traveler, there is typically a sprinkler cart on which the sprinkler is mounted, with a large hose that feeds the sprinkler strung out through the field in the direction of travel that the sprinkler will irrigate, to another cart supporting a hose reel. In operation, the hose reel rotates, pulling the hose in, along with the sprinkler cart. For a typical rectangular field, the farmer would like to start the sprinkler running against the far end or starting point of the field with the sprinkler irrigating a half circle pattern, looking towards the hose reel. After the sprinkler cart is beyond one radius of throw of the far end of the field, the farmer would then like to irrigate an arc of approximately 270xc2x0 with the un-irrigated piece being directly between the sprinkler cart and the hose reel. This is usually the best traveling distribution curve for the sprinkler cart since the path where the sprinkler cart travels remains as dry as possible, and thus helps prevent the sprinkler cart from becoming stuck. As the sprinkler cart approaches the hose reel at the near end of the lot, the farmer would like to again change the sprinkler to a half circle arc such that the sprinkler irrigates into the field and not onto the hose reel, i.e., the half circle arc would extend away from the hose reel and near end of the lot. These arc changes may also involve matters of safety since the ends of the field are often roads or buildings or some other area that it is desired to keep dry.
When the large volume sprinkler is used on the end of pivots, it is often used to increase the acreage of ground covered, particularly in the corners of a rectangular field. By intermittently turning the sprinkler on and off, it can be used to irrigate the corners of a square or rectangular field as the pivot is swung in a circle. This is done by turning the sprinkler on as the pivot enters the corner and turning it off as it leaves. By being able to also vary the arc of travel of the sprinkler as the pivot comes into and out of the corner, and as it travels through the corner, a higher degree of accuracy could be obtained while irrigating more of the ground in the corner area of the field.
The present invention incorporates an arc changer mechanism that allows a large volume sprinkler to operate using different preset arcs of travel in a manner that is simple, reliable, and easy to adjust. The arc changer mechanism is also designed so that it can be easily retrofitted to an existing large volume sprinkler in the field. On present large volume, part circle sprinklers, there is a fixed xe2x80x9ctrip leverxe2x80x9d or lever arm that operates between two stops that determines the arc of travel through which the sprinkler will rotate. In the exemplary embodiment of the invention, the lever arm is adjustable, and by selectively positioning the lever arm such that it works on different stops, the arc of travel of the sprinkler can be changed. The arc changer in accordance with the exemplary embodiment utilizes two hydraulic cylinders (an upper cylinder and a lower cylinder) to move the trip lever between three positions of operation.
More specifically, the trip lever is pivotally mounted to a hub, with a pair of links pivotally mounted at one end on the lever, on opposite sides of the trip lever pivot. Each of the pair of links is attached at opposite ends to pistons slidably supported in the hub for axial movement within hydraulic chambers or cylinders. Depending on which of the pistons is actuated, the trip lever is caused to swing inwardly or outwardly on its own pivot. Thus, the remote end of the lever is moved radially outwardly to a first position when hydraulic fluid is supplied to the lower chamber. The lever is moved radially inwardly to a third position when hydraulic fluid is supplied to the upper chamber. When neither chamber is pressurized, the lever is balanced by springs in an intermediate or second position, radially between the first and third positions.
The stops are designed such that their outside radii are shaped like arcuate cams that correspond to the first, second and third positions of the lever arm. In this regard, the remote end of the lever arm is fitted with a cam roller. During normal rotation through an arc of travel, the cam roller moves through its arc without engaging the adjacent cam surface. However, when the arc changer is actuated to move the lever arm to another position when the sprinkler is in a position that is not already in the range of the new stop set, the roller on the end of the trip lever arm will be forced onto the cam surface of the stop. The sprinkler will continue to operate with the trip lever roller, rolling along the cam surface until it falls within the operating zone, i.e., within the circumferential arc, of the new particular set of stops. If the sprinkler is transitioned into the next set of stops when the lever arm is circumferentially within the arc of the next set of stops, it will change arcs without the roller contacting any of the arc shaped cam surfaces.
As described herein, the sprinkler uses hydraulic cylinders or chambers using water as the working fluid. These cylinders could also be pneumatic, oil hydraulic, or electromechanical. The input for changing the arc may be conventional timers, remote control or hardwired signals operating solenoids or other forms of control valves. The adjustable stops may be made by providing the cams on plates arranged to slide under and/or over each other, thus allowing greater range of arc variation. This allows the end user to easily adjust the sprinkler to their specific application.
According to one aspect, the present invention relates to an actuator assembly for a rotatable sprinkler head having a base supported for rotation on a stationary platform assembly, the actuator assembly comprising a hub mounted for rotation on a shaft supported in said base; a lever arm pivotally mounted at one end to said hub and having a free end extending downwardly toward a stop plate assembly supported on said platform assembly; said stop plate assembly configured to define two or more arcuate paths of travel for said lever arm, said paths being radially offset relative to said hub; and wherein said lever arm is adjustable to selectively locate said free end in any of said two or more arcuate paths of travel.
In another aspect, the invention relates to an actuator assembly for a large volume sprinkler head mounted for rotation relative to a stop plate assembly, the actuator assembly comprising a lever arm on the sprinkler head adapted to cooperate with the stop plate assembly to define different paths of travel for the sprinkler head; the lever arm movable radially between the different paths of travel.
The invention will now be described in greater detail in connection with the various drawing figures identified below.